Background: Silage additives are marketed with the primary aim of improving the fermentation and/or aerobic stability of silage. The objective of this study was to evaluate the impact of three different essential oils (EOs; cinnamon leaf (CIN), oregano (ORE) and sweet orange (SO)) on the fermentation characteristics and stability of barley silage. Chopped whole-plant barley (Hordem vulgare L.) forage was ensiled either untreated (0 mg kg⁻¹ dry matter (DM)) or treated with CIN, ORE or SO (37.5, 75 and 120 mg kg⁻¹ DM).
Results: Moulds were not detected in any treatments, including the control, after 7 days of air exposure. All EOs at a concentration of 120 mg kg⁻¹ silage DM decreased (P = 0.001) yeast populations in comparison with the control during air exposure. Net gas, methane and ammonia concentrations in vitro did not differ among treatments. Changes in volatile fatty acid concentrations were small, and in situ data showed no changes in DM and neutral detergent fibre digestion rates for CIN, ORE or SO at concentrations up to 120 mg kg⁻¹ DM.
Conclusion: The findings from this study show that a concentration of 120 mg EO kg⁻¹ DM decreased yeast counts during aerobic stability tests. However, all EO treatments had minimal effects on data from in vitro and in situ incubations.